During the previous projects period, the biotransformation and fate of xenobiotic chemicals in fish have been intensively studied. The induction of trout hepatic monooxygenases by chemicals and the influence of induction on bioaccumulation of chemicals has been the subject of recent investigations. During the last two years, a cDNA which codes for the hydrocarbon-inducible form of hepatic P1-450 has been developed and the studies in this proposal are designed to further characterize this cDNA and investigate its possible use in an assay to detect exposure of fish to hazardous chemicals in water supplies. This assay could serve as a sentinel in monitoring water for chemicals which could adversely affect human health. The model inducers to be studied include 3- methylcholanthrene (3-MC), beta-naphthoflavone (BNF), 2,3,7,8- tetrachlorodibenzodioxin (TCDD) and 2,3,7,8-tetra- chlorodibenzofuran (TCDF). A second goal in this proposal is to isolate and characterize the forms of P-450 which are present in fish liver and to determine the nature of the biotransformation products they form from specific chemicals. These metabolic products may accumulate in fish destined for human consumption and may differ from those formed in mammalian tissues if the P-450 isozyme profile of fish liver is different from that found in mammals. The chemicals to be studied include chlordimeform, fenitrothion, aldicarb and N- acetylaminofluorene.